Single clutches

[IanHood]

Can anybody here tell me what the difference is between the 350/450 widecase clutch basket and the 250 version? I believe the gear on the crank is the same for all versions so what is different?

Ian

[LaceyDucati]

Ian
The gear sets have different ratios. The crank gear is different on a 250 to a 350/450,as well as the basket.

Nigel

[IanHood]

Ah, that would explain it then. I suspect what I have in my 450 engine is actually a 250 clutch. I do have what I think is a 450 basket in my spares pile but not a crank gear. Do you know what the tooth count for each gear is Nigel (for a 450)?

Ian

[themoudie]

Aye Ian,

As Nigel says, the widecase 239cc and 250cc engines have a primary drive ratio of 2.500:1, as do the narrow case 250cc engines back to the 1961 Monza and Diana (Europe/USA) engines. The 350cc and 450cc engines, starting with the narrow case 1965 - 1967 Sebring 350cc and through to the end of production 1974 350cc and 450cc widecase engines all have a primary drive ratio of 2.111:1.

I am unable to quote the actual number of teeth on the crankshaft helical gear and the clutch baskets number of teeth. Alternatively, they may have the same number of teeth on the gear/clutch basket, but be of differing diameters. Again, I am unable to provide all of that information for you.

However, I have nipped out to the workshop and the O.D. of a late widecase 350cc MKIII engine clutch basket is ~129 mm +/- 0.500 mm, with a tooth count of 57 teeth. I do not have a crankshaft helical gear, or a 250cc widecase clutch basket to hand to give you dimensions or teeth numbers.

Hoepfully, this is sufficient information for you to make a judgement on what primary drive set up you have fitted to your 450cc engine.

Good health, Bill

[IanHood]

Thanks gentlemen. Looks like I am going to have find a 450 crank gear from somewhere. If anyone on here has one spare, please yell.

Ian

[LaceyDucati]

I will look today,I probably have a few as It's the baskets that wear or are damaged.

[IanHood]

Thanks Nigel, much appreciated!

Ian

[Smoggy]

Hi Ian,
I've had a look in a copy of the 1968-73 engine spares catalogue given to me by Mick Walker when I visited him in 1982 to swop a basket case 175 for spares for my valve spring 239cc, being the "Front Counter " copy it has handwritten entries detailing the differing 239 part numbers as well as other odds and sods. The part numbers for the 250 are - crank gear 0403.47.010 , 24 teeth, clutch housing 0600.16.810, 60 teeth, 350/450 crank gear 0606.47.010, 27 teeth, clutch housing 0606.16.810, 57 teeth. My 239 has a 25 tooth crank gear and a 62 tooth clutch housing, as mentioned by Jon Pegler in a previous post, no handwritten entries for part numbers so I assume Mick Walker wasn't aware of the difference from the 250s. There is also a handwritten entry for the 1975/76 450 Desmo Mk 111 clutch housing part number 0615.16.950 , no mention of the number of teeth. Hope this helps.

Regards,
Dave

[Wildcat]

I found this post by using the search function on here a few weeks ago while researching if a 350/450 set would fit my 250.

HTH

[Eldert]

Hi Ian

if Nigel cant find any Z=27 crank gears . i think i have a few laying around

Eldert